Electrical method and apparatus



Feb. 25, 1930. J. KREMER 1,748,927

ELECTRICAL METHOD AND APPARATUS Original Filed DeG- l. 1925 4 sheets-sheet 1 Smuemfoc @W www Feb. 25, 1930. J. KREMER ELECTRICAL METHOD AND APPARATUS Original Filed DGO. l. 1925 4 Sheets-Sheet 2 3 M, v e n i" o z b/HNEM/ZR. wf@

Feb. 25, 1930. J, KREMER 1,748,927

ELECTRICAL METHOD AND APPARATUS Original Filed De0 1. 1925 4 Sheets-Sheet 5 @la ff $7 @iff ww Feb. 25, 1930. J. KREMER 1,748,927

ELECTRICAL METHOD AND APPARATUS Original Filed Dec. l, 1925 4 Sheets-Sheet 4 Patented Feb. 25, 1930 PATENT OFFICE JOHN KREMER, F SOUTHPORT, CONNECTCUI ELECTRICAL METHOD AND APPRATUS Application led December 1, 1925, Serial The flow of an electric current through a conductor having resistance generates a quantity of heat proportional to the square of the quantity of current, the resistance through which it flows and the time of flow. This generation of heat will result in a rise in temperature in the conductor and,l if the heat is not removed at as rapid a rate as it is generated, the temperature will rise sufiiciently high to injure or destroy the conductor or its insulation or the apparatus associated with it. To enable the apparatus to withstand theserheating effects the rate of dissipation or loss of heat must equal that of the generation of heat, and accordingly the current carrying capacity of the apparatus will depend principally on the effectiveness of this cooling or heat dissipation. To secure the largest amount of current carrying capacity, particularly in apparatus in which radiation is obstructed, artificial means are provided to carry the heat away from the conductor, usually by circulating a 'cooling fluid such as air or oil in intimate contact with the surface of the conductor.

In cooling by the use of cooling fluid, the heat must flow from the element in which lit is generated, or the source of heat, into the cooling or heat abstracting fluid under a difference in temperature, or temperature gradient sufficient to overcome the resistance to flow or conduction of heat. The resistance to be overcome includes not only the resistance in passing to the surface of contact with the cooling fluid, but also the much greaterfresistance to flow' of heat offered by a substantially stationary layer of film of the fluid adhering to the surface of the conductor.

In such anarrangement, the current of cooling fluid must be supplied at a rate suiicient 5 to absorb and carry away this heat. The

N'o. 72,611.A Renewed September 10, 1929.

temperature gradient required to carry heat from the interior of an electric conductor into the moving body of cooling fluid is proportional to the quantity of heat being thus transferred in a given time, and when the interior or source of the heat reaches the highest temperature it can withstand, the limit of temperature gradient and of heat transfer, and accordingly of current, is reached.

The necessity of taking heat away from the conductor of an electric circuit limits the current that may pass through the circuit and thus opposes an insuperable obstacle to developments that require a concentration of current beyond the limit thus set. This is particularly the case in electro-magnets in which the electro-magnetic effects are dependent on the quantity of current flowing through the coils of the electromagnet as well as on the number of coils. For example, in the case where an electro-magnetic solenoid is carrying its maximum of current, to double the intensity of magnetism or the mag netic flux, it would be necessary to double the number of turns, which would greatly increase the bulk of the coil. A point is eventually reached, however, when the additional coils interfere with the circulation of the cooling fluid and also where they have such a large diameter that, for a given consumption of power, they do not add greatly to the intensity of the magnetism or to the magnetic flux. The intensity of the magnetic field thus encounters a limiting obstacle, which prevents the attainment of effects, such as the selective attraction or repulsion of gases and of particles having only a slight magnetic susceptibility, which effects are obtained to too slight an extent with the relatively weak fields attainable by apparatus heretofore used.

These obstacles are4 obviated by my present invention, one object of which is to provide electric apparatus in which the electric current carried by the conductor need not be limited by the necessityvof conduct` ing the generated heatfrom its source bythe building up of a temperature gradient.

Other and further features and objects of 2 I 1,74s,ea7

f its conducting and heating generating position to a cooling or heat abstracting position, to provide an electromagnetic apparatus in which a movable or replaceable conductor is arranged to conduct current for a period of time and to be cooled out of the conducting circuit in a succeeding period of time, to provide a fluid conductor and to circulate it alterately into an electric circuit and into a cooling circuit, to provide electric apparatus in which the heat generated by an electric current or by electronic or ionic bombardment is removed together with the conductor from the heat generating zone and cooled outside of said zone, to provide an electromagnetic apparatus in which a magnetic field of substantially unlimited intensity may be obtained and to obtain through this intense magnetic field, magnetic effects, such as the selective attraction and repulsion of gas molecules or of weakly magnetic particles that are not obtainable to a useful extent by the moderate magnetic intensities now available.

Astill further object of the invention is to provide a conductor for electric devices which employ iron to increase the flux density 1n the vicinity of a conductor carrying a current 1n which a cooling ofthe conductor in the apparatus is not essential.

With these and other objects in view, which may be apparent from the following description, the invention comprises the methods and apparatusdescribed and set forth in the following specification and claims.

The temperature to which an uncooled conductor will rise is determined in part by the quantity of heat or energy that is supplied to itand this is in turn determined not only by Y the rate at which the energy is supplied, but

also by the length of time during which the energy is supplled.l If the time during which the electric energy is supplied be made sufficiently short, the electric curr nt that may be sent through the conductor may be made much greater than it could normally carry in continuous operation.

In m present invention, the time during which t e current is flowing through a conductor is made comparatively short, the conductor being circulated into the electric circuit and then substantially out of the circuit and into a cooling medium at such a rate that it remains in the electric circuit too short a time to become overheated. While it is out of the electric circuit the conductor may be cooled in any suitable manner or means or combination of means, as by radiation, conduction or convection, and, by making the time durin which the conductor is out of the circuit and undergoing cooling relatively long as compared with the period of time during whic it is included in the circuit,

roviding a maximum of cooling surface, or

y the use of both of these factors the quantity of current passing through the conductor while in the electric circuit may be made correspondingly large for a given temperature rise. There is therefore no necessity for e001- ing -the conductor while in the electric circuit and the limitations imposed by the necessity of a temperature gradient to cause a flow of heat from its source do not appear.

The circulating conductor may be of any suitable type, either solid, liquid or gaseous, havin a conductivity not less than one thousandt that of mercury, but because of their flexibility and facility in circulating, fluid conductors are generally preferred. Any metal that is liquid at the working temperatures may be employed, for example, mercury or a suitable alloy at atmospheric temperatures or above, or, at higher temperatures, a fusible alloy or metals such as sodium or other alkali, or alkali earth metals or alloys may be used. When sodium or a similar liquid is used, it may be circulated through tubes or conduits of iron, or other suitable material either conducting or non-conducting and is circulated in a sealed circuit so that it cannot become exposed to the air or to moisture. Preferably the conduit will be made of nonconducting materiaL When a metallic or conducting conduit is used it may be so proportioned that it carries a minimum of current, or so slight a proportion of the current that the heat generated within it is quickly absorbed by the circulating liquid conductor or the surrounding atmosphere, or both, and its temperature therefore does not rise much above that of the circulating liquid conductor nor to its melting or destruction temperature. Although the use of molten sodium requires a minimum temperature somewhat above the normal atmospheric temperatures, it has the advantages of a low resistance relative to its volume as compared with mercury and its melting point of 97 degrees C. isls'ufliciengyV rings or circuits contacting and joined in the electric circuit and spreading out, for example, into the atmosphere or into a cooling fluid outside of the electric circuit to provide a maximum of heat dissipating surface and the fluid is circulated through these rings successively from the electric circuit to the cooling circuit and returned.

Various features of my invention are illustrated in the accompanying drawings, in which: y Fig. l is a somewhat diagrammatic sectional view of an electromagnet embodying a form of my invention.

Fig. 2 is a view substantially on the line 2-2 of Fig. 1. p

Fig. 3 is a perspective view of the coils of the electro-magnet shown insomewhat separated position.

Fig. 4 is a view of a fragment of an electromagnetic and circulating system' embodying a modified form of the invention. Y Fig. 5 is a view, partly in section, of a fragment of an electromagnet coil embodying a modified form of the invention in which the conducting liquid is circulated transversely of the electric current, and

Fig. 6 is a cross sectional view of a pair of electrodes embodying ano-ther form of the y invention.

Fig. 7 is a longitudinal sectional View through an electromagnetic coil embodying a modified form of the invention.

Fig. 8 is a cross sectional view of the coil taken on line 8-8 of Fig. 7

Fig. 9 is a longitudinal sectional view of a solenoid embodying a modified form of the invention.

Fig. 10 is a longitudinal sectional view o-f a portion of a modified conduit and cooling loop or circuit, and

Fig. 11 is a diagrammatic view of a transformer embodying my invention.

In the embodiment of the invention illustrated in Figs. l, 2 and 3 of the accompanying drawings, the fluid conductor. fused sodium or its equivalent, is circulated from a storage tank or receptacle 2O through an outlet pipe 21 to the innermost turn 22 of a coil 23 formed of a length of pipe coiled in the proper or desired manner. lf the pipe is made of conducting material, or if the pipe is made of non-conducting material, but does not sufficiently insulate one conductor turn from an adjacent turn, the adjacent turns of the coil may be separated by a strip of mica or other suitable insulating material, solid, liquid or gaseous, capable of withstanding the moderately high temperatures of the coil. The sodium or other circulating conductor flows through the pipe of the coil from the innermost turn to the outermost turn 24, from which it fiows through an extension 25 of the pipe forming the coil into a second or receiving tank or re eptacle 26. In some cases the fluid may, of course, fiow from the outer to the inner turn, or through but a part of the coil.

Electric current may be supplied to the tank 2O througha main 27, indicated diagrammatically in the drawing, or to the pipe 21, and withdrawn from the pipe 25 or tank 26 through a return main 28, or the current in ay be sent through the coil in the reverse direction, as` circumstances may render desirable. rllhe tanks 20 and 26 are insulated from each other, except through the conducting coil or coils.

The fluid metal supplied from the tank 20 through the coil 23 to the tank 26 must be returned to the tank 2O in order that the cycle of the fluid may be completed. This may be done in any suitable manner as, for example, by passing the fluid metal through an interrupting apparatus in which the continuity of the metal stream is broken up into insulated portions, or in any other suitable manner that will prevent the `coil 23 from being short circuited. The same result is, however, preferably accomplished without the necessity for an interrupting apparatus by means of the arrangement shown in Figs. l, 2 and 3 of the drawings, in which a second pipe coil 29 is provided immediately adjacent to, but electrically insulated from, the coil 23 by a plate of insulating material 30, and having its turns wound reversely to those of the coil 23 so that, although the current may enter at the outermost turn and flow towards the innermost turn, the fiow of the current in the turns of both coils is the same and, accordingly, magnetism of like polarity is generated by each coil. The innermost turn of the coil 29 is then connected to the tank 26 by means of a connecting pipe extension 3l and the outermost turn is connected to the tank 20 by means of a pipe extension 32. It will bc understood, therefore, that the fiuid conductor is returned to the tank 20 through the coil 29 at approximately the same rate as it is passing through the coil 23 to the tank 26, that the electric current divides, one part flowing through the coil 23 and the other part flowing through the coil 29, and that, accordingly, the tanks are kept at their proper voltages without the use of an interrupting device. It will be understood, of course, that the turns of the coil 29 may be separated by air or by an insulating strip 33 similarly to the insulating of the turns of the coil 23. It will also be understood that when the coils and their magnetic effects are sufficiently separated they may both be wound in any desired manner.

rl`he`passage of current through the coils 23 and 29 generates considerable heat in the fluid conductor fiowing therethrough so that' the fluid delivered by the outlet pipes 25 Jand 32 to the tanks 26 and 20, respectively, must be cooled before being returned to the respective coil supply pipe connections 21 and 31. To this end fiuid may be continuously withdrawn from the uppermost part of the tank 20 through a'pipe 34, passed through a cooling apparatus, not shown, and returned to the lower portion of the tank through a return pipe 35, which extends downwardly lso ` a suitable cooling returned to the 'bottom portion of the tank.

in the tank 20 to but a short s ace from the bottom. Similarly, heated uid is withdrawn from the upper portion of the tank 26 through an outlet pipe 36, passed through apparatus, not shown, and

through a pi e 37, extending to very nearly the bottom o the tank. Any suitable cooling apparatus may be employed, such for example, as ipes 91 exposed to the atmosphere so that t ere may be a sufficiently rapid radiation of heat, or a heat exchanger cooled by means of a cooling fluid, or in some cases the tanks themselves may provide sufficient cooling through radiation of heat. The heat thus generated may, of course, be applied for useful industrial effects. In any event the cooling should not be sufficient, when using a fusible-metal or alloy, as to permit the solidification of the fluid conductor. In some cases the tanks may be omitted and the fluid circulated directly from the electromagnetic coils to the cooling system.

The shape and arrangement of the wind-` ings 23 and 29 are such as are required by the particular purposes for which the apparatus is to`be used. In the example shown in the drawings, a simple type of coil is shown in which the turns of the coil are formed of uniform, flattened pipes or tubes made continuous with the pipe portions 21, 25, 31 and 32. It is to be understood, however,thatv these windings may be madev of nonuniform dimensions, as for example, the outer turns may be made larger, and that the turns of pipe may also be given a shape other than that shown in the drawings, wherever the requirements of the apparatus should make that desirable.

The quantity of current that may be passed through the coils 23 and 29 is limited only by the heating of the circulating conducting fluid' to the maximum temperature that it will stand without deterioration or destruction of the apparatus. The temperature rise caused by a given current on the circulating conducting fluid may be decreased by increasing the speed of circulation of the fluid and thereby decreasing the period of time during which it is in the coils 23 and 29 and subjected to the heating effects of the electric current. The electric current capacity of the coils is therefore limited only by the speed with which the conducting fluid may be circulated, the cooling effect to which the fluid withdrawn from the tanks 2() and 26 may be subjected being substantially unlimited.

In some cases, as indicated in Figs. 1, 2 and 3, a sufficiently rapid circulation may be obtained without the necessity of positive pumping means, by a proper use of the reciprocal repelling action of the fluid on the walls of the coils or of the fluid in the respective turns of the coils, or both. Thus. in the coils of Figs. 1, 2 and 3, the current flowing `drives the fluid metal to the outermost turn and draws a new supply of metal to the innermost turn. For example, the portions of currents flowin in opposite directions on opposite halves o the turns of the coil repel each other, exerting an outward force on the fluid. As the diameter of the -coil constantly increases, the conduit diverges slightly from a right angle to the radius and the outward force is thus partially resolved lengthwise of the conduit. With the heavy currents that may be employed, this lengthwise resolved force may be quite appreciable. In some instances this repelling effect may give all of the circulation required. In other instances, however, where a greater circulation is required, a pump 38, or other circulating device, may be interposed in the pipe 21 or pipe 31, as shown in Fig. 4, a by-pass pipe 39 eing provided around the pipe and having a cut-off or stop valve 40.

In the form of embodiment shown in Figs. 1, 2, 3 and 4, the length of the uncooled circulating circuit of the conducting fluid in the turns of the coil is equal to or greater than the length of the electric circuit comprised by the coil. The length of flow of the circulating conducting fluid in the conducting portion may, however, be made much shorter than the length of the electric circuit by the arrangement or embodiment of the invention shown in Fig. 5. In this embodiment, of which but a section of a portion of the coils is illustrated in the drawing, the conducting fluid is circulated in a path transversely of the electric circuit, the fluid passing from an edge of each of the turns, 41, 42, 43, etc., of the coil through closed pipes or tubes 44, 45 and 46, respectively, to the opposite edge to again enter the respective turns and pass transversely therethrough. The fluid thus circulates through the closed circuits 44, 45, 46, etc., being heated by the current in the portion of its circuit comprised in the turns 41, 42 and 43 and cooled in the outer portions 44, 45 and 46, which are ex osed to cooling by radiation or by a cooling uid. If the circulation be at all rapid, the length of time that the fluid is in the conducting portion is so short that the electric current may be increased to almost any desired limit without danger of overheating. A small lengthwise circulation of the conducting fluid is not detrimental and may be provided to eliminate any pockets of fluid in the electric conducting path. The tube portions 44, 45and 46 are spaced so closely on their respective turns 41, 42 and 43, however, that they are substantially contacting at the electric conducting or turn portions, and accordingly but a very slight longitudinal circulation is required.

The fluid may be circulated in the circulating and cooling tube portions 44,45 and 46, respectively, by any suitable means, but preferably by reciprocal electro-magnetic repulsion effects similar to those indicated above. For example, the walls of the turn portions may be tapered or otherwise arranged to provide for a resolution of outward force longi tudinally of the path of travel of the fluid.

The conducting means provided by my invention may also be applied to the supplying of current to electrodes Without excessive heating, as for example, in the manner shown diagrammatically in Figure 6. In these electrodes, the circulating fluid returning from a cooling system, through a pipe 49 enters an outer end of an electrode at one side of an internal longitudinal partition 50, and flows through a compartment 5l formed by this partition to the inner or arcing end of the electrode. At this arcing or inner end, the conducting fluid is subjected to the intense heat of the are 52 as well as to the heating effect of the electric current supplied to the electrode and becomes heated. As the fluid reaches the arcing end of the electrode, it flows through an opening` or space 53 into a return compartment 54 at the other side of the partition, and returns to the outer end of the electrode and passes out through an outlet pipe 55 to return to the cooling apparatus. The other or complementary electrode 56 may be similarly provided with an inlet pipe 57, partition 58 and outlet pipe 59, or may be of the standard or of any suitable type.

In the coil shown in Figs. 7 and 8 the repelling effect of theneighboring currents on each other is utilized to circulate the flowing liquid transversely of the turns of the coil and throu h the cooling system. For this purpose tIle turns 61 of' the coilare made flat and of an approximately frustro conical shape, one edge 62 of each turn being of smaller d1- ameter than the other edge 63 so that the repelling forces of' the currents in the turns of the coils are resolved into a transverse force as well as an outward one that drives the fluid from the edge 62 to the opposite edge 63 of the larger diameter. From the edge 63 the fluid is received into a series of cooling and return tubes 64, leaving at an angle to give a greater deflection to the departing streams of fluid, then sweep through a cooling loop to return to the edge 62 and be sent again through the turn of the coil.

In this arrangement, the current 1s led into, or from, the inner turn of the coil through a number of segmental mains 65, 66, 67 and 68, four being shown on each face of the coil by way of example, the cross sectional area of the mains increasing rapidly from the juncture with the edge 63 or edge 62 xso that the density of the current is relatively low, and conducting fluid is circulated through these mains in a manner similar to that of the cooling and return tubes 64, thus serving to keep the mains cool, as well as to increase the cooling and circulation of the fluid. It will be noted also in this gure that the dimensions of the turns of the coils increase as their diameter increases, thus making it possible to get a stronger field with a given consumption of' powers,

In Fig. 9 a solenoid is illustrated in which the expanding ,action of an electric loop is utilized -to circulate the conducting fluid. In this modification` of the invention, the conduits conveying the conducting fluid are arranged in the form of a solenoid of a conical or frustro-conical shape. Four sets of conductor coils 69, 70, 7l and 72 are used and are coiled in turns of expanding or increasing diameters from the inlet end 73 of the solenoid to the outlet end 74, the turns of the conductor conduits being placed closely adjacent so that they form a compact frustroconical structure. The adjacent turns of the respective sets of coils may be separated by suitably coiled strips 75, 76, 77 and 78 of suitable insulating material, and the adjacent layers of conduits may be separated by conical sheets of insulation 79, 80 and 8l so that there may be no short circuiting of' the turns of the coils. The conducting Huid that leaves the outlet og larger diameter end 74 of the solenoid returns through a suitable cooling circuit, not shown, to the inlet or smaller end 73 of the solenoid. In this solenoid, also, the outer conduits or turns are made of larger diameter thanthe inner conduits in accordance with approved theory. l

To enable current to be used with greater voltages, the inner pair of conduits 69 and 70 are connected in series with the outer pair 71 and 72 by means of a connecting member or plate 82, the other ends of the conduits 69 and 7 O being connected to a main 83 and the other ends of the conduits 7l and 72being connected to a main 84.

In the above embodiments the conducting fluid has been illustrated as circulated by the expanding action of a currentwon a loop or turn. 'Ihis is to be taken, however, as illustrative, it being understood that when this action is not eflective or is not desired, that mechanical means such as a suitable pump, may be employed, or the fluid may be circulated by a moving or rotating magnetic field, or other means.

In the examples mentioned above the fluid conducting metal has either been circulated through the entire portion of the conduit in which the electric current is conducted before being re-cooled or has been sent transversely of the direction of the electric current. This is not essential to the invention, however, as the metallic fluid may be Isent through a portion of the electric conductin path, then withdrawn and cooled and passe through a succeeding portion of the circuit.

This may be, for example, in the construction shown in Fig. 10 in which a conduit'85 is provided with a metallic or conducting partition 86 through which the electric current readily passes, but which shunts the circulating conducting fluid through a cooling` l tion of the arrow in Fig. 10 isdeflected by the partition 86 into the cooling circuit 87 is cooled and returned on the opposite side of the partition 86 to continue through the conduit. To enable the loop 87 to leave and enter the conduit 85 .it the samevplace in the length of the conduit, the partition 86 is inclined as indicated.

The circulating fluid conductor may also be used as a winding or windings in electric power generating, transforming or utilizing apparatus, as in dynamos or generators, transformers or motors. Thus, as shown in Fig. 11, in which the invention is embodied in a transformer shown diagrammatically, a core 88 of iron or equivalent magnetic material provided with a suitable secondary winding 89 is provided withl a hollow conduit 90 through which a conducting fluid is circulated to and from a cooling means and is connected in an electric circuit to act as the primary coil of the transformer. It is, of course, obvious that either the primary or secondary coil, or both, may be constructed of the circulating fluid conductor. l

As the field associated with the electric current may have sufficient collapsing effect on the Walls of the confining conduit to injure them if they are electrically conducting, or the stream of liquid conductor itself may be pinched in by the electric current, it may be desirable in some cases to impose a pressure on the fluid in the apparatus to overcome this effect. In the use of sodium, also, it may be necessary to provide an expansion chamber filled with an inert gas, as indicated at 92 in Fig. 4 to prevent the bursting of the apparatus as the sodium melts, inasmuch as sodium expands on melting.

Molten sodium may in cases be used to advantage where the cooling takes place in the electric circuit itself, the convection in a fluid medium such as molten sodium being more effective for the transfer of heat than conduction to which the transfer of heat in solid 'conductors is limited.

Inasmuch as the effective heating action of a current may be rendered negligible for a given current through my above described invention, the current densities may be greatly increased, not onlywhere magnetic fields of exceptional intensity are desired, but also in cases in which a high concentration or density of current is required for other purposes, as

is sometimes the casein X-ray machine. For example, if it is required to pass an extremely large current to or from a discharge or receiv ing point, or a conductor approximating a point, the current may be led thereto through converging conduits and led therefrom through diverging conduits, and a conducting fluid passed through these conduits so that a high velocity is created in the conducting point that effectively dissipates the heat generated in this fluid. Or, where the current is to be assed through a point, either to be discharged or received at a physical point, it may be passed from a hemispherical or equivalent source radially to the point through a mass of the metallic conducting fluid rapidly flowing or sweeping past the point and thus continuously replaced and kept cool regardless of the density of the current.

The intense magnetic fields or fluxes made possible by my invention make it possible, by passing a mixture of particles or gases in a stream adjacent the field, to separate the particles, droplets or gases in cases where the particles or gases are insufficiently magnetic to enable this to be done by the magnetic fields now available. In such separations, the more magnetically susceptible particles are attracted to or repelled from the passing stream into or out of the field of greatest intensity and 'then withdrawn.

The invention may also be applied, when desired, to the cooling of motors or generators, using the circulating fluid in suitable conduits as the conductors of the rotor or stator. When used in motors, particularly, the use of the fluid obviates the necessity for a resistance circuit in starting. It is also applicable for creating an intense field where desired for sensitive galvanometers, or other apparatus of a scientific or industrial character in which a high magnetic flux is desired.

As changes could be made within the scope of my invention, it is desired that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

Having now described my invention, what I claim as new and desire to secure by Letters Patent is:

1. Apparatus of the type described which comprises, a conduit, a body of sodium in said conduit, means for circulating said sodiumin said conduit, and means for conducting electric current through said circulating sodium'.

2. Apparatusyof the ty e described which comprises, a conduit, a bod )yy of sodium in said conduit, means for passing electric current through said sodium, and means for circulating said sodium in said conduit transversely of said electric current.

3. Apparatus of the type described which comprises, a conduit formed into the shape of an electro-magnetic solenoid, means for circulating molten sodium through .said conduit, means for receiving molten sodium from said conduit, and means for passing an electi'ic current tlii'ough the molten sodium Within said conduit.

4. An electric conductor comprising a conduit filled with sodium, means for circulating said sodium in'a fused state through said conductor, and means for cooling said sodium. z

5. Apparatus of the type described which comprises, a hollow conduit coiled into turns of progressively increasing diameters to form a solenoid of a substantialy conical lform, means for circulating an electrically conducting fluid through said conduit, and means for conducting an electric current through said fluid.

6. Apparatus of the type described which comprises, a hollow inner conduit c oiled into adjacent turns of progressively increasing diameters longitudinally of the turns, a conduit of larger diameter coiled about the turns of said inner conduit,means for circulating separate streams of an electrically conducting fluid through saidconduits, and means for connecting said streams in series in an electric circuit. l

f 7. Apparatus of the type described which comprises, a pair of electric terminals, a pair of hollow conduits connecting said terminals in parallel, means. for circulating a conducting fluid from one terminal to the other` terminal through one conduit and returning the conducting fluid to the firstqterminal through the other conduit, said conduits being formed into electro-magnets having the same polarity when connected in parallelin an electric circuit, and means for cooling fluid at each of said terminals.

8. Apparatus of the type described which comprises a conduit, a body of metallic sodium filling said conduit, means for circulating said sodium in molten condition through said conduit, and means for varying a magnetic flux through said circulating molten sodium to set up an electric current flow in the circulating sodium.

9. Apparatus of the type described, which comprises a pluralityof conduits connecting two electric terminals, means for circulating a fluid from one terminal to the other terminal through one conduit and returning the fluid conductor to the first terminal through another conduit, means for cooling said fluid conductor at one of the terminals, and means for passing an electric current between the terminals through the fluid within the conduits substantially to the exclusion of the conduits.

10. Electrical apparatus comprising, in combination, a magnetic core forming part of a magnetic circuit, a non-conducting conduit wound 1n the field of said magnetic circuit,

a conducting fluid within said conduit, means for circulating said fluid through said conduit, and means for connecting saidfluid in an electric circuit, the fluid acting as a conductor for the electric current substantially to the exclusion of the conduit.

11. Apparatus of the type described which comprises a conduit, a body of sodium in said conduit, means for circulating said sodium in said conduit, means for cooling said sodium, and means for conducting an electric current through said circulating sodium.

12. An electric conductor comprising a conduit filled with sodium, and means for circulating said sodium in a fused state through said conduit.

13. Apparatus of the'type described which comprises, in combination, a conduit for an electric conducting fluid, a cooling system for said electric conducting fluid, an electric conducting fluid within said conduit and said cooling system, means for circulating said fluid through said conduit and said cooling system, and electrical connections to said Huid for causing an electric current to pass therethrough within said conduit substantially to the exclusion of said conduit.

14. Apparatus of the type described, which comprises, in combination, an electric nonconducting conduit, an electric conducting fluid within said conduit, means for circulating said fluid through said conduit, means for cooling said fluid, and electrical connections for causing an electric current to pass through the fluid within said conduit.

v 15. Apparatus of the type described which comprises, in combinationa conduit for an electric conducting fluid, an electric conducting fluid flowing through said conduit, said conducting fluid and said conduit respectively having large current carrying capacity and small current carrying capacity, means for passing an electric current into and thro-ugh said conducting fluid Within said conduit, means for cooling said conducting fluid, and means for circulating said fluid through said conduit and said cooling means.

16. The method of cooling an electric `conductor which comprises removing the conductor from an electric circuit while maintaining the electric circuit unbroken, cooling the electric conductor, and returning the electric conductor to the electric circuit.

17. The method of cooling a fluid electric conductor forming a portion of an electric circuit which lcomprises removing the fluid conductor from the electric circuit while maintaining the electric circuit unbroken, cooling the fluid conductor, and returning the fluid conductor to the electric circuit.

18. Apparatus of the type described which comprises, in combination, a mobile electric conductor, means for supporting said mobile conductor as an electrically continuous body in an electric circuit, means for removing a portion of sai-d mobile conductor from said circuit whih` maintaining the continuity of said circuit, means for cooling the mobile condnitor removed from the circuit, and means for returningr the cooled conductor to the electric circuit.

19. Apparatus of the type described which comprises, in combination, a mobile electric coinluctor, means for supporting said lnobile conductor between the terminals of an external electric circuit, means for causing said mobile conductor to pass between and beyond the terminals of the external circuit, the arrangement being such that the mobile conductor is the primary electric current carrying medium connectin the terminals, and means for cooling said mobile conductor when not between said terminals.

20. Apparatus of the type described, which comprises, in combination, a conduit for a mobile electric conducting medium, a cooling system for said mobile conducting medium, a mobile electric conducting medium within said conduit and said cooling system, means t'or circulating said mobile conducting medium through said conduit and said cooling systcm, and electrical connections between the mobile conducting medium and an external clectrie circuit, the arrangement being such that the electric current owing in said external circuit and through said mobile conducting medium is carried by the mobile conducting medium substantially to the exclusion of the conduit.

21. Apparatus of the type described, which comprises, in combination, two separated electric terminals, a mobile electric conducting medium for contact therewith, means for causing a portion of the mobile electric conducting medium to move between and beyond said terminals in an electrically continuous body, means for cooling said portion of the mobile conducting medium when not between said terminals, and means for causing said cooled portion to be again moved between said terminals.

In testimony whereof, JOHN KREMER has signed his name to this specification this 30th day 0f November', 1925.

- JOHN KREMER. 

